Low Molecular Weight Fraction Research Articles

Influence of Wax Inhibitor Molecular Weight on Solution Crystallization and Rheology of Monodisperse Waxes

Molecular weight fractionation via stepwise precipitation or chain scission is performed on four pour point depressant polymers to study the pour point reduction mechanism. An homologous series of model oils is prepared by dissolving 5 wt % of a single-component paraffin wax (n-C24, n-C28, n-C32, or n-C36) in n-C12. The polymers are dosed at 500 ppm in the model oils and moderately reduce crystallization temperatures by elevating the nucleation barrier. Polymers containing carboxylate or acrylate moieties also modestly enhance equilibrium wax solubility. Reduction in crystallization temperature is largely independent of polymer molecular weight, except for carboxylate polymers where low molecular weight fractions are largely ineffective. In general, model fluids containing shorter wax chains show a larger reduction in crystallization temperature than model fluids containing longer wax chains. However, yield stress reduction often shows a distinct dependence on polymer molar mass. Low molecular weight fractions of carboxylate and acrylate polymers provide smaller reductions in yield stress than the overall parent fraction. Cross-polarized microscopy reveals that polymers reduce the crystal size, alter the crystal morphology from platelet to needle-like, and induce branching. Crystal branching and formation of dendrite-like structures result from strong polymer binding at the wax crystal interfaces. Hence, single-component wax crystal branching occurs phenomenologically along with yield stress reduction.

Different level of tumor necrosis factor-a expression after administration of silk sericin fraction in RAW264.7 cells

Tumor necrosis factor-α (TNFα) is a representative marker for inflammation. Silk sericin is known as mild TNFα inducer. The purpose of this study was to compare the level of TNFα among different fractions of silk sericin. Silk sericin was extracted from cocoon and separated it by molecular weight. Each fraction was applied to RAW264.7 cells. The level of TNFα was evaluated by western blot and ELISA assay. In results, the level of TNFα was increased as time-dependent manner. Higher molecular weight fraction of sericin induced higher amount of TNFα than lower molecular weight fraction. In conclusion, different molecular weight fraction of sericin induced TNFα differently.

Revealing the membrane fouling mechanism caused by the denitrification filter effluent during ozonation by model assessment

Abstract Membrane fouling has been a major obstacle for stable operation of ultrafiltration. In this study, prevailing fouling models were applied to assess the fouling behavior of the denitrification filter (DNF) effluent during ozonation. In order to clarify the fouling mechanism, correlation analysis and redundancy analysis (RDA) were conducted to investigate the correlations among model parameters, fouling potential and water features of the DNF effluent. The combined intermediate-standard model exhibited superior determination coefficients (R2 > 0.99). Based on analytical results, the model parameter of intermediate blocking (Ki) and standard blocking (Ks) was fairly applicable to describe the fouling of higher molecular weight (F1, MW >4,000 Da) and lower molecular weight fractions (F2, MW = 2,000–4,000 Da and F3, MW < 2,000 Da), respectively. In comparison, F1 played a predominant role in the fouling behavior of the DNF effluent. Increased ozone dosage resulted in decreased membrane fouling contribution of F1 and increased fouling contribution of F2 and F3 during ozonation. The change of fouling contributions was attributed to the transformation of high MW fractions into lower MW fractions by ozonation. This study clarified the relationships between model parameters and the membrane fouling process caused by organic fractions with specific molecular weight, thus demonstrating the membrane fouling mechanism of the DNF effluent during ozonation.

The effect of a color tattoo on the local skin redox regulatory network: an N-of-1 study

Biomedical aspects of tattooing have been extensively discussed in literature, however pathophysiological effects of tattoo inks in the human body are still unexplored. Oxidative stress is considered responsible for the adverse effects of tattooing, however no experimental evidence for tattoo ink-related oxidative stress in the human body currently exists. The aim was to examine the effect of a blue tattoo on skin redox regulatory network (RRN) parameters in a single human subject. Skin surface oxidation-reduction potential (ORP) was analyzed with a PH60F flat probe. Interstitial and intracellular fluid enriched capillary blood from the tattoo and the control area was extracted and analyzed with I2/KI-stabilized microORP, nitrocellulose redox permanganometry (NRP), carbonato-cobaltate (III) formation-derived H2O2 dissociation rate assay, 1,2,3-trihydroxybenzene autoxidation assay, thiobarbituric reactive substances (TBARS) assay and 5,5,’-dithio-bis-(2-nitrobenzoic acid) (DTNB)-based determination of free thiol content in low molecular weight and protein precipitate fractions. Surface ORP analysis revealed a greater antioxidant capacity of tattooed skin in comparison with the control (CTR). Capillary blood analysis confirmed greater reductive capacity in the tattoo sample both by microORP (−4.33 mV vs CTR) and NRP (+10.8%). Hydrogen peroxide dissociation rate (+11.8%), and protein sulfhydryl content (+8.5%) were increased, and lipid peroxidation (−15%) was reduced in the tattoo sample in comparison with the CTR. In this N-of-1 study, RRN of tattooed skin was shifted toward a more reductive state with all parameters indicating reduced levels of oxidative stress in comparison with nontattooed skin. The local antioxidant effect of copper(II) phthalocyanine provides one possible explanation of the observed effects.

Influence of PLGA molecular weight distribution on leuprolide release from microspheres

Poly (lactide-co-glycolide) (PLGA) is a biodegradable copolymer used in many long-acting drug products. The objective of the present study was to investigate the influence of polymer molecular weight distribution differences of PLGA on the in vitro release profile of leuprolide acetate microspheres. Eight microsphere formulations were prepared using the same manufacturing process but with different PLGA polymers. The physicochemical properties (drug loading, particle size and morphology) as well as the in vitro release profiles of the prepared microspheres were evaluated using a sample-and-separate method. The amount of burst release increased with increasing amount of low molecular weight fractions of PLGA, indicating that the drug release profiles appeared to be affected not only by the average molecular weight but also the molecular weight distribution of PLGA. In conclusion, quality control of the molecular weight distribution of PLGA as well as the weight average molecular weight is highly desirable in order to control the burst release.

Isolation and Assessment of a Highly-Active Anti-Inflammatory Exopolysaccharide from Mycelial Fermentation of a Medicinal Fungus Cs-HK1.

The purpose of this work was to fractionate the complex exopolysaccharide (EPS) from a medicinal fungus Ophiocordyceps sinensis Cs-HK1 based on the molecular weight (MW) range and to assess the in vitro anti-inflammatory activity of different EPS fractions in THP-1 cell culture. The lower MW fraction (EPS-LM-1) showed a much higher anti-inflammatory activity. EPS-LM-1 was identified as a heteropolysaccharide consisting of mannose, glucose, and galactose residues with an average MW of 360 kDa. EPS-LM-1 significantly inhibited the lipopolysaccharide-induced inflammatory responses with the effective concentrations for 50% inhibition below 5 µg/mL on a few major proinflammatory markers. With such a notable in vitro anti-inflammatory activity, EPS-LM-1 is a promising candidate for the development of a new anti-inflammation therapy.

Subsea permafrost as a potential major source of dissolved organic matter to the East Siberian Arctic Shelf.

Arctic subsea permafrost contains more organic carbon than the terrestrial counterpart (~1400 Pg C vs. ~1000 Pg C) and is undergoing fast degradation (at rates of ~10 to 30cmyr-1 over the past 3 decades) in response to climate warming. Yet the flux of organic carbon sequestered in the sediments of subsea permafrost to overlying water column, which can trigger enormous positive carbon-climate feedbacks, remain unclear. In this study, we examined the dissolved organic matter (DOM) diffusion to bottom seawaters from East Siberian Sea (ESS) sediments, which was estimated at about 943-2240g C m-2yr-1 and 10-55g C m-2yr-1 at the continuous-discontinuous transition zone of subsea permafrost and the remainder shelf and slope sites, respectively. The released DOM is characterized by prevailing dominance (≥ 98%) of low molecular weight (Mn<350Da) fractions. A red-shifted (emission wavelength >500nm) fluorescence fingerprint, a typical feature of sediment/soil DOM, accounts for 4-6% and 7-8% in the fluorescence distributions of seawaters and pore waters, respectively, on ESS shelf. Statistical analysis revealed that seawaters and pore waters possessed similar DOM composition. The estimated total benthic efflux of dissolved organic carbon (DOC) was ~0.7-1.0 Pg C yr-1 when the estimate was scaled up to the entire Arctic shelf underlain with subsea permafrost assuming the width of continuous-discontinuous transition zone is 1 to 10m. This estimation is consistent with the established ~10-30cmyr-1 degradation rates of subsea permafrost by estimating its thaw-out time. Compiled observation data suggested that subsea permafrost might be a major DOM source to the Arctic Ocean, which could release tremendous carbon upon remineralization via its degradation to CO2 and CH4 in the water column.

Investigation of characteristics of effluent DON derived from conventional activated sludge (CAS) and predenitrification biological removal (BNR): In terms of proteins and humic substances

Upgrading wastewater treatment plants (WWTPs) from conventional activated sludge (CAS) to predenitrification biological nutrient removal (BNR) results in improved removal of dissolved inorganic nitrogen (DIN) from wastewater. However, changes in dissolved organic nitrogen (DON) with these WWTP upgrades and their potential impacts on receiving waters have been little researched. In this study, we investigated characteristics of effluent DON derived from CAS and predenitrification BNR, paying special attention to proteins and humic substances. Through a lab-scale reactor study and analysis of full-scale WWTP effluents, we found that in predenitrification BNR effluent, proteins are much more dominant than humic substances, whereas in CAS effluent, proteins and humic substances are similarly abundant. In terms of molecular weight, the majority of proteins were present in the effluent's low molecular weight (LMW) fraction (<1 kDa), while humic substances were found mostly in the effluent's high molecular weight (HMW) fraction (0.45 μm–1 kDa). Determination of dissolved organic carbon (DOC)/DON ratios in effluents supports that proteins (and LMW-DON) were most likely microbial-derived organic N produced during treatment processing, whereas humic substances (and HMW-DON) more likely originated outside of treatment systems. Bioassay tests demonstrated that effluent DON derived from predenitrification BNR was more bioavailable than that derived from CAS. We also found that LMW-DON and proteins were highly bioavailable DON compared to HMW-DON and humic substances. The results of this study suggest that upgrading CAS to predenitrification BNR makes effluent DON to become more conducive to phytoplankton blooms in receiving waters.

Peptidomic analysis of low molecular weight antioxidative peptides prepared by lotus (Nelumbo nucifera Gaertn.) seed protein hydrolysates

Lotus (Nelumbo nucifera Gaertn.) seeds are rich in proteins and are considered to be a beneficial source of plant proteins. In this study, lotus seed protein hydrolysate (LSPH) was prepared using Flavourzyme and antioxidant activities were evaluated. The LSPH possessed the highest DPPH-scavenging (EC50 2.9 mg/mL), H2O2-scavenging (EC50 16.1 mg/mL), and reducing power activity (8.0 mg/mL) at 180 min of hydrolysis. After gel filtration and reverse phase HPLC purification, the low molecular weight fraction was then analyzed by Nano-LC-MS/MS. Sixteen peptides with corresponding mass from 1 to 2 kDa were identified. Peptides with hydrophobic features and acidic amino acids, Asp and Glu, are considered to contribute to overall antioxidant activities. These results show Flavourzyme hydrolysis of lotus seed protein successfully generates low molecular fragments that make them a potential nutraceutical or health promoting supplement.

Production and Fractionation of Rocky Shore Crab (Grapsus albacarinous) Protein Hydrolysate by Ultrafiltration Membrane: Assessment of Antioxidant and Cytotoxic Activities

ABSTRACT Bioactive peptides from marine protein sources hold tremendous promise as potent antioxidant agents with plausible anticancer activity. Herein, the antioxidant activities of crab protein hydrolysate and its ultrafiltration fractions at different molecular weights (>30 kDa,10–30 kDa,3–10 kD and<3 kDa) using various methods (DPPH, ABTS and FRAP assay) were investigated carefully. The results showed that although all peptide fractions from the crab hydrolysate showed some activity, the low molecular weight fractions (3–10 kDa and <3 kDa) generated the highest antioxidant activity, with a high content of hydrophobic amino acids (48.87% for 3–10 and 46.26% for <3 kDa). Interestingly, both low molecular weight peptide fractions showed a remarkable cytotoxic effect against the MCF-7 cells, while the 3–10 kDa peptide fraction proved to be more effective. Phase-contrast microscopy of treated MCF7 cells with the 3–10 peptide fraction confirmed various morphological alterations and cell damages. Overall, the study suggested that the low molecular weight peptide fractions of rocky shore crab Grapsus albolineatus hydrolysate could be considered as a natural antioxidant candidate in the prevention of cancer by reducing free radicals production, as well as an anticancer agent in cancer treatment by cytotoxic effect on cancer cells.

A new approach to recycling cephalosporin fermentation residue into plant biostimulants

Cephalosporin fermentation residue (CFR), a byproduct of the pharmaceutical industry, mainly contains the mycelial biomass and unutilized culture medium, which can be reused as a high-quality protein source. This study first reports the recycling CFR into plant biostimulants using partial acid hydrolysis. Temperature, reaction time and ratio of hydrochloric acid/dry matter (H/S) were optimized for yielding both free amino acid and low molecular weight fraction based on response surface methodology. The crude protein concentration of CFR is 55%, with glutamic acid being the dominant amino acid (12.5%). Two favorable hydrolysis conditions were obtained: (1) 140 °C, 10.7 h, 17 H/S for maximizing the amino acid yield of 45.5 g/100 g CFR dw and (2) 100 °C, 10.7 h, 19 H/S for maximizing the low molecular weight fraction of 28.2%. The CFR-derived biostimulants obtained from two optimum conditions possessed two biostimulant modes of action: plant growth promotors/inhibitors and stress alleviators. However, they showed the differences in aminograms and profiles of low molecular weight compounds. Neither residual cephalosporin C nor its byproduct was detected in the CFR-derived biostimulants, suggesting that partial acid hydrolysis appears capable of recycling CFR into plant biostimulant safely.

Active Human and Porcine Serum Induce Competence for Genetic Transformation in the Emerging Zoonotic Pathogen Streptococcus suis.

The acquisition of novel genetic traits through natural competence is a strategy used by bacteria in microbe-rich environments where microbial competition, antibiotics, and host immune defenses threaten their survival. Here, we show that virulent strains of Streptococcus suis, an important zoonotic agent and porcine pathogen, become competent for genetic transformation with plasmid or linear DNA when cultured in active porcine and human serum. Competence was not induced in active fetal bovine serum, which contains less complement factors and immunoglobulins than adult serum and was strongly reduced in heat-treated or low-molecular weight fractions of active porcine serum. Late competence genes, encoding the uptake machinery for environmental DNA, were upregulated in the active serum. Competence development was independent of the early competence regulatory switch involving XIP and ComR, as well as sigma factor ComX, suggesting the presence of an alternative stress-induced pathway for regulation of the late competence genes required for DNA uptake.

Effect of oxidation ditch and anaerobic-anoxic-oxic processes on CX3R-type disinfection by-product formation during wastewater treatment

The high chlorine dosages in wastewater treatment plants during the COVID-19 pandemic may result in increased formation of disinfection by-products (DBPs), posing great threat to the aquatic ecosystem of the receiving water body and the public health in the downstream area. However, limited information is available on the effect of biological wastewater treatment processes on the formation of CX3R-type DBPs. This study investigated the effect of oxidation ditch (OD) and anaerobic-anoxic-oxic (AAO), two widely used biological wastewater treatment processes, on the formation of five classes of CX3R-type DBPs, including trihalomethanes (THMs), haloacetic acids (HAAs), haloacetaldehydes (HALs), haloacetonitriles (HANs) and halonitromethanes (HNMs), during chlorination. Experimental results showed that biological treatment effectively reduced the dissolved organic carbon (DOC) and UV254, while it increased the dissolved organic nitrogen (DON), and therefore the ratio of DON/DOC. In addition, increases in the contents of soluble microbial product- and humic acid-like matters, and the transformation of high molecular weight (MW) fractions in the dissolved organic matter into low MW fractions were observed after OD and AAO processes. Although biological treatment effectively decreased the formation of Cl-THMs, Cl-HAAs, Cl-HANs and Cl-HNMs, the formation of DBCM, DBAA, BDCAA, DBCAA, DCAL, TCAL and DBAN (where C = chloro, B = bromo, D = di, T = tri) all increased significantly, due to the increased formation reactivity. Moreover, biological treatment increased the ratio of bromide/DOC and bromine incorporation into THMs, HAAs and DHANs except for HALs and THANs. Different from previous studies, this study revealed that biological treatment increased the formation of some DBPs, especially brominated DBPs, despite the efficient removal of organic matters. It provides insights into the DBP risk control in wastewater treatment, particularly during the COVID-19 pandemic.

Size and resin fractionations of dissolved organic matter and characteristics of disinfection by-product precursors in a pilot-scale constructed wetland

Abstract Controlling the formation of disinfection by-products (DBPs) is a major issue in the drinking water industry, and understanding the characteristics of DBP precursors in treatment processes for micro-polluted raw water is key to improving water quality. In this study, a sampling program was undertaken to investigate the fate of dissolved organic matter (DOM) and the characteristics of DBP precursors in a pilot constructed wetland imitating the Yanlong Lake ecological project. Using XAD resin adsorption and ultrafiltration techniques, the dissolved organic carbon, UV254, and DBP formation potential (DBPFP) were measured in different DOM fractions in raw water and wetland effluents. After the constructed wetland treatment, the low molecular weight fraction (&amp;lt;3 kDa) of DOM and DBPFP generally showed a decreasing trend along the water path, while the high molecular weight fraction (&amp;gt;3 kDa) of DOM increased. The specific DBPFP (SDBPFP) was much higher in the &amp;lt;1 kDa fraction than in the other fractions. Although the hydrophobic fraction of DOM was the most abundant in all stages of the wetland treatment, the SDBPFP of the hydrophilic fraction was higher than that of the hydrophobic fraction. Furthermore, compared with raw water, the DOC, UV254 and DBPFP in the treated wetland effluents increased; however, all of the chemical DOM fractions exhibited decreased SDBPFP in accordance with a decrease in the specific ultraviolet absorbance during wetland treatment. These conclusions indicate that the DOM produced by the wetland system may generate DBPs less readily compared with the DOM of raw water.

Study of the composition of low-molecular compounds in the oligomethylhydridesiloxanes

The presence of reactive hydrogen-silyl (SiH) bonds in oligomethylhydrosiloxanes provided their widespread use in the building, paper, textile and rubber industries. Low molecular weight fractions of methylhydrosiloxanes, both cyclic and linear, negatively affect the performance of oligomer-based materials. The main goal of the present study is detection and identification of these fractions in the commercial product 136-157M, as well as in the co-oligomers synthesized from it. A method of gas chromatography-mass spectrometry was used in the study. First, we proved that an increase in the temperature of the column and evaporator from 60°C to 300°C does not change the composition of the low molecular weight fractions. Consequently, no depolymerization processes related to the formation of low-molecular-weight compounds occur during the analysis. To perform a qualitative analysis, the components of low-molecular-weight fraction were separated on a capillary column and then identified using a mass detector with an ion trap. It is shown that electron ionization triggers fragmentation of molecules and the formation of positively charged ions. As for methylhydrosiloxanes, cations with a molecular weight of [M – 15] + arising from the rupture of the carbon-silyl bond are formed first. Moreover, when such a rupture occurs in cyclosiloxanes with a total number of units of more than four, further dissociation processes can occur with the detachment of the neutral fragment (methylsilane) and the formation of bicyclosiloxane cations. Since the set of positive ions is individual for each of the components and depends on [M] +• , a component-wise description of the entire low molecular weight fraction becomes possible with a high degree of the reliability. It is sown that for the considered commercial sample it can be described by two homologous series — cyclic where m ≥ 4, and linear siloxanes where n ≥ 1

Effects of ultrasound on the enzymatic degradation of pectin

Ultrasound-assisted enzymatic maceration (UAEM) has gained considerable interest in the fruit juice industry, owing to its potential to increase juice yield and content of polyphenols while simultaneously saving time and energy. In this study, the effects of UAEM (ultrasonic probe, 20 kHz, 21 W*cm−2 and 33 W*cm−2) on pectin degradation in a continuous circulation system were investigated over 60 and 90 min. Main pectinolytic enzymes activities of (polygalacturonase, pectin lyase and pectin methylesterase) of a commercial enzyme preparation were examined for individual synergistic effects with US. Pectin hydrolysis by UAEM differed significantly compared to treatment with ultrasound or enzymes alone regarding the profile of degradation products compared to treatment with ultrasound or enzymes alone. Ultrasound fragmented pectin to less branched oligomers of medium molecular weight (Mp approx. 150 kDa), which were further degraded by pectinolytic activities. The low molecular weight fraction (<30 kDa), which is known to be beneficial for juice-quality by adding nutritional value and stabilizing polyphenols, was enriched in small oligomers of homogalacturonan-derived, rhamnogalacturonan I-derived, and rhamnogalacturonan II-derived residues. Synergistic effects of ultrasound application enhanced the effective activities of polygalacturonase and pectin lyase and even prolonged their performance over 90 min, whereas the effective activity of pectin methylesterase was not affected. Final marker concentrations determined by each enzyme assay revealed a considerable higher total process output after UAEM treatment at reduced temperature (30 °C) comparable to the output after conventional batch maceration at 50 °C. The obtained results demonstrate the high potential of UAEM to produce high-quality juice by controlling pectin degradation while reducing process temperature and equally highlight the matrix and enzyme specific effects of a simultaneous US treatment.

Molecular weight-dependent abundance, absorption, and fluorescence characteristics of water-soluble organic matter in atmospheric aerosols

Water-soluble organic matter (WSOM) plays a significant role in solar radiative forcing and atmospheric chemistry. Its chemical composition and properties are highly molecular weight (MW)-dependent, but are still poorly understood. In this study, 10 PM2.5 samples were collected at a rural site in China, and the WSOM therein was fractionated into three MW fractions, >5 kDa (F1), 1–5 kDa (F2), and <1 kDa (F3), using an ultrafiltration (UF) system. The abundance, optical properties, and fluorescence properties of the three MW fractions were comprehensively determined using a total organic carbon (TOC) analyzer, ultraviolet–visible (UV–vis) spectroscopy, and excitation-emission matrix (EEM) fluorescence spectroscopy combined with parallel factor (PARAFAC) modeling. The proportional TOC and Abs365 distributions of the MW fractions were F1:F2:F3 ≈ 24:22:54 and 40:24:36, respectively. This suggested that the major OC species in bulk WSOM were partitioned into the low MW (<1 kDa) fraction, while the major light-absorbing chromophores were partitioned into the large MW (F1 + F2, >1 kDa) fraction, and were especially prevalent in the >5 kDa fraction. The optical parameters, i.e., SUVA254 and MAE365, generally increased with the apparent increase in MW, suggesting that the higher MW fractions might have a stronger aromaticity and light absorption capacity. The EEM-PARAFAC analysis identified three humic-like substances (HULIS) (C1–C3) and one protein-like (C4) substance for all MW fractions, of which the proportional distributions were observed as C1:C2:C3:C4 ≈ 20:24:41:15, 21:23:44:12, and 41:22:13:24 for F1, F2, and F3, respectively. This indicated that the >1 kDa fraction was enriched in highly-oxygenated HULIS (C3), whereas the <1 kDa fraction had more less-oxygenated HULIS (C1) and protein-like (C4) substances than the >1 kDa fraction. The study provided a detailed insight of the MW-dependent characteristics of WSOM by reducing their heterogeneity and complexity, which is of great significance for further understanding the chemical properties and structures of WSOM.

Neuroprotection mediated by ST266 requires full complement of proteins secreted by amnion-derived multipotent progenitor cells.

ST266 is the biological secretome of cultured Amnion-derived Multipotent Progenitor cells containing multiple growth factors and cytokines. While intranasally-administered ST266 improves the phenotype in experimental optic neuritis, specific ST266 components mediating these effects are not known. We compared the effects of ST266 with and without removal of large molecular weight proteins both in vitro and in the multiple sclerosis model experimental autoimmune encephalomyelitis (EAE) in C57BL/6J mice. Mice were treated daily with intranasal vehicle, ST266 or lower molecular weight fraction of ST266. Retinal ganglion cells were counted in isolated retinas, and optic nerves were assessed for inflammation and demyelination. ST266 treatment significantly improved retinal ganglion cell survival and reduced optic nerve demyelination in EAE mice. The lower molecular weight ST266 fraction significantly improved optic nerve demyelination, but only showed a trend towards improved retinal ganglion cell survival. ST266 fractions below 50kDa increased Schwann cell proliferation in vitro, but were less effective than non-fractionated ST266. Demyelination attenuation was partially associated with the lower molecular weight ST266 fraction, but removal of higher molecular weight biomolecules from ST266 diminishes its neuroprotective effects, suggesting at least some high molecular weight proteins play a role in ST266-mediated neuroprotection.

Effects of colloidal TiO&lt;sub&gt;2&lt;/sub&gt; particles on photodegradation of dissolved organic matter from different sources: Based on molecular weight difference analysis

溶解性有机质（DOM）广泛存在于多种水环境介质，其光降解过程显著影响水体污染物的化学形态及生态风险.本文以典型陆源天然有机质（NOM）和藻源有机质（AlgOM）为研究对象，采用切向超过滤技术将初始DOM样品（Bulk，<0.45 μm）分为高分子量（HMW，1 kDa~0.45 μm）和低分子量（LMW，<1 kDa）组分，研究胶体TiO₂颗粒存在下不同分子量有机组分的光降解行为差异.表征结果表明，DOM样品的有机质均相对较多地分布在LMW组分中（55.3%~57.8%），但HMW的芳香性比LMW组分高；三维光谱结果表明AlgOM富含类蛋白和类腐殖物质，而NOM只含类腐殖物质；进一步分析发现类蛋白物质主要分布于HMW组分，类腐殖物质则主要分布于LMW组分.胶体颗粒的存在通过吸附作用抑制AlgOM中有机质及芳香性物质的光降解，而通过催化作用促进NOM中有机质及芳香性物质的光降解.胶体颗粒不改变不同分子量DOM中有机质的光降解效率顺序，均为HMW>Bulk>LMW，说明HMW有机质更易光降解.但无胶体颗粒时AlgOM和NOM芳香物质的光降解效率为LMW>Bulk>HMW，且胶体颗粒的存在改变不同分子量NOM芳香性物质的光降解顺序.另外，无胶体颗粒存在时陆源类腐殖物质比藻源类腐殖物质更易光降解，而胶体颗粒的存在均可促进藻源和陆源类腐殖质物质光降解；相比于HMW类腐殖质，LMW类腐殖物质具有较高的光敏性和优先降解特性.;Dissolved organic matter (DOM) exists widely in water environmental media, and its photodegradation process significantly affects the chemical species and ecological risk of pollutants in waters. This study took the typical terrestrial natural organic matter (NOM) and algal-derived organic matter (AlgOM) as the research objects, fractionating the initial DOM sample (Bulk, <0.45 μm) into high molecular weight (HMW, 1 kDa-0.45 μm) and low molecular weight (LMW, <1 kDa) fractions via tangential ultrafiltration technique, to analyze the difference of photodegradation behavior of organic components with different molecular weights in the presence of colloidal TiO₂ particles. The characterization results showed that organic matter of DOM samples was relatively more distributed in LMW components (55.3%-57.8%), but HMW was more aromatic than LMW components. Three-dimensional fluorescence spectrum showed that AlgOM was rich in protein-like and humus-like substances, while NOM only contained humus-like substances. Further analysis revealed that protein-like substances were mainly distributed in HMW components, and humus-like substances were mainly distributed in LMW components. The presence of colloidal particles promoted the photodegradation of organic matter and aromatic substances in NOM by catalytic effect, while inhibited the photodegradation of organic matter and aromatic substances in AlgOM by adsorption effect. Colloidal particles did not change the photodegradation efficiency order of organic matter in DOM with different molecular weights, all of which were HMW>Bulk>LMW, indicating that HMW organic matters were easier to be photodegraded. However, without colloidal particles, the photodegradation efficiency of AlgOM and NOM aromatics was LMW>Bulk>HMW, and the presence of colloidal particles changed the photodegradation order of NOM aromatics with different molecular weights. In addition, terrestrial humus was more easily degraded than algal humus in the absence of colloidal particles, and the presence of colloidal particles promoted the photodegradation of both algal and terrestrial humus. Compared with HMW humus, LMW humus had higher photosensitivity and preferential degradation characteristics.

Comparison of alcalase- and pepsin-treated oilseed protein hydrolysates – Experimental validation of predicted antioxidant, antihypertensive and antidiabetic properties

There is emerging evidence on the importance of food-derived bioactive peptides to promote human health. Compared with animal derived proteins, plant proteins, in particular oilseed proteins, are considered as affordable and sustainable sources of bioactive peptides. Based on our previous bioinformatic analysis, five oilseed proteins (flaxseed, rapeseed, sunflower, sesame and soybean) were enzymatically hydrolysed using alcalase and pepsin (pH 1.3 and pH 2.1). Further, low molecular weight (Mw ​< ​3 ​kDa) fractions were generated using ultrafiltration. The protein hydrolysates and their low Mw fractions were evaluated for their in vitro antioxidant, antihypertensive and antidiabetic capabilities, in comparison with samples obtained from two dairy proteins (whey and casein). Apart from dipeptidyl-peptidase IV inhibition, significantly stronger bioactivities were detected for the low Mw fractions. In partial agreement with in silico predictions, most oilseed hydrolysates exerted comparable angiotensin-converting enzyme inhibitory capability to dairy proteins, whilst whey protein was the most promising source of dipeptidyl-peptidase IV inhibitors. Apart from alcalase-treated soybean, dairy proteins were more efficient in releasing antioxidant peptides as compared to oilseed proteins. On the other hand, soybean protein hydrolysates showed the highest α-glucosidase inhibitory activity amongst all protein sources. Overall, there was limited correlation between in silico predictions and in vitro experimental results. Nevertheless, our results indicate that oilseed proteins have potential as bioactive peptide sources, and they might therefore be suitable replacers for dairy proteins as well as good sources for development of functional foods.